Plasma membrane vesicles isolated from rat liver cells have been subjected to four different agents in attempts to promote their fusion with artificial lipid vesicles so as to alter the lipid composition of the plasma membrane vesicles. Short chain alkanes were better "fusogens" than lysolecithin, Ca ion at high pH or sonication of the artificial lipid vesicles. Actual merger of the plasma membrane vesicles with artificial lipid vesicles was indicated by means of differential scanning calorimetry and density gradient centrifugation. Binding of fluorescent concanavalin A and agglutination by concanavalin A of unadulterated plasma membrane vesicles was greater than of such vesicles in the presence of lipid vesicles or of plasma membrane vesicles fused with artificial lipid vesicles by hexane treatment. Hexane treatment did not cause the fused plasma membranes to lose significant amounts of protein as judged by polyacrylamide gel electrophoresis.